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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4957af79365sm6222315e9.9.2026.07.23.09.34.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jul 2026 09:34:56 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 23 Jul 2026 18:34:56 +0200 Message-Id: To: "Maxim Khmelevskii" , "Alexei Starovoitov" , "Andrii Nakryiko" , "Daniel Borkmann" Cc: , "Ilya Leoshkevich" , "Heiko Carstens" , "Vasily Gorbik" , "Alexander Gordeev" Subject: Re: [PATCH bpf-next] selftests/bpf: Fix flaky refcount asserts in map_kptr_race From: "Kumar Kartikeya Dwivedi" X-Mailer: aerc 0.21.0 References: <20260723114042.559926-2-max@linux.ibm.com> In-Reply-To: <20260723114042.559926-2-max@linux.ibm.com> On Thu Jul 23, 2026 at 1:40 PM CEST, Maxim Khmelevskii wrote: > bpf_testmod shares objects across tests; prog_test_struct that holds > cnt.refs.counter is one of them. Refcounter release is deferred behind > an RCU grace period, so it may still be pending when this test asserts. > wait_for_refs prevents flaky failures when other tests have contaminated > the refcount. > > Fixed tests: > - test_htab_leak > - test_percpu_htab_leak > - test_sk_ls_leak > > Reported-by: Ilya Leoshkevich > Reviewed-by: Ilya Leoshkevich > Signed-off-by: Maxim Khmelevskii > --- Wouldn't this still be flaky? Could we order these tests and wait for a RCU= gp to pass before finishing each one? We have kern_sync_rcu(). Either way, I d= on't think the current approach is the right way forward. pw-bot: cr > .../testing/selftests/bpf/prog_tests/map_kptr_race.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/tools/testing/selftests/bpf/prog_tests/map_kptr_race.c b/too= ls/testing/selftests/bpf/prog_tests/map_kptr_race.c > index 506ed55e8528..5a543b3465a8 100644 > --- a/tools/testing/selftests/bpf/prog_tests/map_kptr_race.c > +++ b/tools/testing/selftests/bpf/prog_tests/map_kptr_race.c > @@ -28,6 +28,15 @@ static int read_refs(struct map_kptr_race *skel) > return skel->bss->num_of_refs; > } > > +static void wait_for_refs(struct map_kptr_race *skel) > +{ > + for (int i =3D 0; i < 500; i++) { > + if (read_refs(skel) =3D=3D 2) > + return; > + usleep(10 * 1000); > + } > +} > + > static void test_htab_leak(void) > { > LIBBPF_OPTS(bpf_test_run_opts, opts, > @@ -73,6 +82,7 @@ static void test_htab_leak(void) > sched_yield(); > > ASSERT_EQ(watcher->bss->map_freed, 1, "map_freed"); > + wait_for_refs(watcher); > ASSERT_EQ(read_refs(watcher), 2, "htab refcount"); > > out_watcher: > @@ -134,6 +144,7 @@ static void test_percpu_htab_leak(void) > sched_yield(); > > ASSERT_EQ(watcher->bss->map_freed, 1, "map_freed"); > + wait_for_refs(watcher); > ASSERT_EQ(read_refs(watcher), 2, "percpu_htab refcount"); > > out_watcher: > @@ -195,6 +206,7 @@ static void test_sk_ls_leak(void) > sched_yield(); > > ASSERT_EQ(watcher->bss->map_freed, 1, "map_freed"); > + wait_for_refs(watcher); > ASSERT_EQ(read_refs(watcher), 2, "sk_ls refcount"); > > out_watcher: